/Engine/Source/Runtime/MeshDescription/Public/MeshAttributeArray.h
Obtain a reference to this with GetAttributesRef>(...)
template<typename T, typename [TEnableIf](API\Runtime\Core\Templates\TEnableIf)< std::is_same_v< typename [TMeshAttributesRegisterType](API\Runtime\MeshDescription\TMeshAttributesRegisterType)< T >::RealAttributeType, int >, int >::Type> TMeshAttributesArray< typename [TMeshAttributesRegisterType](API\Runtime\MeshDescription\TMeshAttributesRegisterType)< T >::RefType > RegisterIndexAttribute ( const [FName](API\Runtime\Core\UObject\FName) AttributeName, const int32 NumberOfChannels, const EMeshAttributeFlags Flags )